The \(z\)  position of the \(\pi ^0 \rightarrow \gamma \gamma \)  decay vertex is computed from photon candidate positions and energies assuming the nominal \(\pi ^0\)  mass [1]}.
It is required to be at least 2 m downstream of the final beam collimator to suppress
\(\pi ^0\)  production in the material of the collimator (Fig. REF ). In addition, photons are
required not to intercept DCH beam pipe flanges [2]}.
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